It is well known to use toner particles stored within a development apparatus in an electrostatographic reproduction machine, such as a copier or printer, to develop electrostatically formed latent images on an image-bearing member. The toner particles may be stored as such alone or as a component of a two-component developmer material, the second component being magnetic carrier particles.
Typically, the development apparatus so used is elongate front-to-back, and is utilized to store, move and mix the developer material. Where two component developer material is employed, moving, mixing and feeding the developer material as such, triboelectrically and appropriately charges the toner and carrier particles therein. Additionally, the development apparatus also brings the developer material into applying relationship with the images to be developed so that the charged toner particles contained in such developer material are attracted to such images. Such development apparatus are disclosed, for example, in commonly assigned U.S. Pat. Nos. 5,025,287; 4,633,807; 4,634,286; and 4,707,107.
The quality of images developed with charged toner particles as above, depends significantly on the effectiveness and reliability of the development apparatus in triboelectrically charging the toner and carrier particles, and in consistently maintaining desirably high end to end concentration levels of toner particles even when new toner particles are replenished or added at one of such ends. As such, improvements in devices for moving and mixing developer material are very important and welcome towards improving the quality and reliability of electrostatographic image development.
It has been found, however, that development apparatus which include conventional and other types of developer material moving and mixing devices, for example, ribbon blenders, helixes and stemmed paddle augers, require jointing and assembly, and hence are likely to experience assembled component failure, thus resulting in occasional and unpredictable moving or pumping of developer material within the development apparatus. Such uneven pumping or movement of developer material is often accompanied by excessive dusting within the development apparatus, by inadequate mixing and, hence, by inadequate charging of the toner and carrier particles therein. More importantly, such uneven movement or pumping of developer material results in dead spots, in uneven front-to-back accumulation, and in uneven depletion of toner particles across the length of the development apparatus. The end result, of course, is occasional poor and unreliable quality development of images.
These shortcomings of the above types of development apparatus have been found to be especially true when the developer material is of the type disclosed in commonly assigned U.S. Pat. No. 4,546,060 issued Oct. 8, 1985 in the names of Miskinis et al. Such developer material as disclosed is comprised of insulative toner particles and of carrier particles exhibiting hard magnetic properties.